The present invention relates to a process to mask non-relevant measured values in an unbalance signal consisting of a large number of measured values as well as a circuit arrangement for carrying out the process.
In determining the unbalance of an object in terms of angle position and magnitude, an attempt is made to determine exclusively the oscillations caused by the effect of the unbalance and their position with respect to a reference point as free of error as possible. The oscillations stemming from the unbalance, however, are always superposed by so-called interference oscillations which can be caused, for example, by processing machines, by passing transportation units, by impact on the machine, and by the drive motor as well as by the bearings of the balancing machine itself. These interferences can strongly falsify the result of the unbalance measurement. In order to mask such interference oscillations, which also include oscillations that occur during the acceleration or deceleration of the object to be balanced, until now the entire measuring range has been divided into a start-up phase in which no measurements were made, a measuring phase in which the unbalance effects and their position with respect to a reference point were picked up and which extended over a certain period of time, followed by the braking phase during which likewise no measurements were made (German patent A-16 48 336).
In another method (German patent A-33 42 542), in order to avoid interference oscillations, the entire measuring procedure was not evaluated if it turned out that the unbalance measurement had been affected by interference oscillations caused by outside influences.
With the measurements carried out according to the state of the art, in the case of German patent A-16 48 336, it cannot be ruled out that, due to unexpected interference effects during the measuring cycle, an erroneous measurement will occur because of which, especially with mass production, a rotatable object measured under these circumstances will be rejected as unusable, even though the unbalance present in the object still falls within a range that would have allowed the object to be used. Such erroneous measurements occur not only with the measurement of mass-produced goods which are balanced in one or two planes, but also with rotatable components, for example, vehicle wheels with tires, which have to be adjusted or completely balanced again at regular intervals in order to eliminate oscillations in the vehicle caused by the unbalance.
In the case of German patent A-33 42 542, the complete measured result is canceled if a permissible interference variable is surpassed, but this necessarily requires another measurement for which it likewise cannot be ruled out that interference variables will not re-occur, thus once again leading to the cancellation of the measured value. This automatically leads to unacceptably time-consuming measurement procedures.
Moreover, with both of these measuring methods, it is not possible to determine interference oscillations, especially in the start-up phase, which can continue on into the measuring phase, thus causing an erroneous measurement, and to mask them as non-relevant measured values.